Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, Via Felice Casorati 43, 37131, Verona, Italy.
Laboratory of Neuromotor Physiology, IRCCS Fondazione Santa Lucia, Rome, Italy.
Exp Brain Res. 2024 Aug;242(8):1881-1902. doi: 10.1007/s00221-024-06866-z. Epub 2024 Jun 14.
Muscle synergies are defined as coordinated recruitment of groups of muscles with specific activation balances and time profiles aimed at generating task-specific motor commands. While muscle synergies in postural control have been investigated primarily in reactive balance conditions, the neuromechanical contribution of muscle synergies during voluntary control of upright standing is still unclear. In this study, muscle synergies were investigated during the generation of isometric force at the trunk during the maintenance of standing posture. Participants were asked to maintain the steady-state upright standing posture while pulling forces of different magnitudes were applied at the level at the waist in eight horizontal directions. Muscle synergies were extracted by nonnegative matrix factorization from sixteen lower limb and trunk muscles. An average of 5-6 muscle synergies were sufficient to account for a wide variety of EMG waveforms associated with changes in the magnitude and direction of pulling forces. A cluster analysis partitioned the muscle synergies of the participants into a large group of clusters according to their similarity, indicating the use of a subjective combination of muscles to generate a multidirectional force vector in standing. Furthermore, we found a participant-specific distribution in the values of cosine directional tuning parameters of synergy amplitude coefficients, suggesting the existence of individual neuromechanical strategies to stabilize the whole-body posture. Our findings provide a starting point for the development of novel diagnostic tools to assess muscle coordination in postural control and lay the foundation for potential applications of muscle synergies in rehabilitation.
肌肉协同作用被定义为具有特定激活平衡和时间分布的肌肉群的协调募集，旨在产生特定于任务的运动指令。虽然姿势控制中的肌肉协同作用主要在反应性平衡条件下进行了研究，但肌肉协同作用在自愿控制直立站立中的神经机械贡献仍不清楚。在这项研究中，研究了在维持站立姿势时，躯干在产生等长力时的肌肉协同作用。要求参与者在腰部水平的八个水平方向上施加不同大小的拉力，同时保持稳态直立站立姿势。通过非负矩阵分解从 16 个下肢和躯干肌肉中提取肌肉协同作用。平均 5-6 个肌肉协同作用足以解释与拉力大小和方向变化相关的各种肌电图波形。聚类分析根据参与者的相似性将肌肉协同作用分为一大组聚类，表明使用主观的肌肉组合来产生站立时的多向力矢量。此外，我们发现协同作用幅度系数余弦方向调谐参数的值在参与者之间存在特定的分布，这表明存在个体神经机械策略来稳定整个身体的姿势。我们的研究结果为开发新的诊断工具以评估姿势控制中的肌肉协调性提供了起点，并为肌肉协同作用在康复中的潜在应用奠定了基础。
